1. Field of the Invention
Aspects of the present invention relate to a wireless communication apparatus and method using a multiple-input and multiple-output (MIMO) method.
2. Description of the Related Art
A multiple-input and multiple-output (MIMO) method is a technology that is used to accelerate communication speed between wireless apparatuses. The MIMO method inputs and outputs a signal by using a plurality of antennas. A characteristic of the MIMO method is that plural pieces of transmission data can be simultaneously transmitted by using different antennas. Accordingly, as the number of channels that can simultaneously transmit data increases, the amount of information that can be transmitted per unit time also increases according to an increased number of channels. Also, according to the MIMO method, the number of frequency bands that are occupied does not increase as the communication speed increases.
However, since a plurality of modulating signals having a carrier wave component of the same frequency is simultaneously transmitted, a receiving apparatus requires a device to separate mixed modulating signals. Accordingly, the receiving apparatus estimates a channel matrix that shows a transmission characteristic of a wireless transmission path, and separates a transmission signal corresponding to each sub-stream transmitted from a transmitting apparatus, from a reception signal based on the estimated channel matrix. The channel matrix is estimated by using a pilot signal, or the like. The pilot signal is a signal already known by the receiving and transmitting apparatuses, and the receiving and transmitting apparatuses can estimate the channel matrix by transmitting and receiving the pilot signal.
However, specific research is required to realize a high precision transmission signal corresponding to a sub-stream by sufficiently removing effects of noise added in the transmission path and interference generated between sub-streams.